Some of my gameworld organizations, such as the clerics of certain evil deities, do use the word "evil" to refer to themselves. They just don't consider it a value judgement. Instead, it's only a marker of which team they're on. They're exactly as comfortable being called "the forces of Evil" as they would being called "the red team" or "the guys in black armor."
If you asked such a cleric about good and evil, he'd give you an explanation about semantics and stolen words, and how the overculture has perverted the meaning of the word "evil." He'll tell you that the majority deities, the "good" ones, have convinced people that "evil" is bad and harmful, when in fact it's just a minority point of view.